1. Field of the Invention
The present invention relates to an antiglare film to be provided on the surface of a window, display etc. In particular, it relates to an antiglare film to be provided on the front surface of such displays as a liquid crystal display (LCD), cathode-ray tube (CRT) display, plasma display (PDP), organic electroluminescence display (ELD) and field effect display (FED, SED). Further, it relates to an antiglare file to be provided on the front surface of a display of a laptop PC or desktop personal computer.
2. Description of the Related Art
Displays such as a liquid crystal display, CRT display, EL display and plasma display have some problems described below from the viewpoint of visibility.                External light reflects at looking and listening.        Surface glare (scintillation) occurs at the display surface by display light from the display.        Visibility is not good caused by dazzle of display light directly coming from the display without being diffused, etc.        Visibility is also degraded by such defect as unevenness of brightness.        
In order to solve such lowering or degradation of visibility, it is known to arrange an antiglare film on the front face of a display.
As an antiglare film, for example, following techniques are known:                To arrange, on the surface of a display, an antiglare film having an antiglare layer having been subjected to embossing finish.        To arrange, on the surface of a display, an antiglare film having an antiglare layer on the surface of which is formed irregularity by mixing particles in a binder matrix.        
In such antiglare film, scattering phenomenon (surface diffusion) of light caused by surface irregularity is utilized.
Further, such antiglare film is also known that, by mixing particles having a refraction index different from that of a binder matrix into the binder matrix, utilizes internal scattering (internal diffusion) of light based on the difference in refraction indices of the binder matrix and particles.
In an antiglare film on the surface of which is formed irregularity through embossing finish, the surface irregularity thereof can be completely controlled. Consequently, reproducibility is good. However, when there is a defect or an adhered foreign substance on an emboss roll, endless defects occurs at the pitch of roll.
On the other hand, an antiglare film using a binder matrix and particles can be manufactured through a smaller number of processes than the antiglare film using embossing finish. Accordingly, it can be manufactured inexpensively. Therefore, various embodiments of antiglare film are known (Patent Document 1).
As for an antiglare film using a binder matrix and a particle, various technologies are disclosed, for example, the following technology is disclosed:                A technique in which binder matrix resin, spherical particles and amorphous particles are used in combination (Patent Document 2).        A technique in which binder matrix resin and plural particles having different particle sizes are used (Patent Document 3).        A technique including surface irregularity, wherein the cross-sectional area of the concave portion is defined (Patent Document 4).        
In addition, the following techniques are disclosed:                A technique wherein internal haze (cloudiness) is 1-15% and surface haze (cloudiness) is 7-30% by using internal scattering and surface scattering in combination. (Patent Document 5)        A technique wherein, while using binder resin and particles having the particle size of 0.5-5 μm, the difference in refraction indices of the resin and the particle is 0.02-0.2 (Patent Document 6).        A technique wherein, while using binder resin and particles having the particle size of 1-5 μm, the difference in refraction indices of the resin and the particle is 0.05-0.15. Further, techniques defining a solvent to be used, surface roughness etc. (Patent Document 7).        A technique wherein, using binder resin and plural types of particles, the difference in refraction indices of the resin and the particle is 0.03-0.2 (Patent Document 8).        
There are also known following techniques that reduce lowering of contrast, hue variation etc. when a viewing angle is altered. In the technique, the surface haze (cloudiness) is 3 or more. Further, the difference between the haze value in the direction of normal line and the haze value in the direction of±60° is 4 or less (Patent Document 9).
As described above, there are disclosed antiglare films of various constitutions for various purposes.
The performance required for an antiglare film differs depending on displays when it is used on the front face of a display. For example, the optimum antiglare film differs depending on the resolving power of a display, intended purpose etc. A broad range of antiglare films are required according to intended purposes.
An antiglare film prevents external light from reflecting by scattering light incident on an antiglare layer. Therefore, in a case where external light reflection preventive property is increased, an antiglare film tends to be whitened. In these years, an antiglare film without white blur, that is, with less white blur tends to be desired according to the change of consumer's tastes. However, as mentioned above, as for an antiglare film, the external light reflection preventive properties and the whitening degree were in a trade-off relation. In a case where enough antiglare property was achieved, an antiglare film tended to be whitened. Conversely, in a case where the whitening was controlled, the external light reflection preventive properties were not achieved sufficiently. The purpose of the present invention is to provide an antiglare film which is superior in external light reflection preventive properties without the whitening.
[Patent Document 1] JP-A-6-18706
[Patent Document 2] JP-A-2003-260748
[Patent Document 3] JP-A-2004-004777
[Patent Document 4] JP-A-2003-004903
[Patent Document 5] JP-A-11-305010
[Patent Document 6] JP-A-11-326608
[Patent Document 7] JP-A-2000-338310
[Patent Document 8] JP-A-2000-180611
[Patent Document 9] JP-A-11-160505